In
computer networking
A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ...
, the ICMP Internet Router Discovery Protocol (IRDP), also called the Internet Router Discovery Protocol,
is a protocol for computer hosts to discover the presence and location of
routers on their
IPv4 local area network
A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building. By contrast, a wide area network (WAN) not only covers a larger ...
. Router discovery is useful for accessing computer systems on other nonlocal area networks.
The IRDP is defined by the IETF RFC 1256 standard,
with the
Internet Control Message Protocol (ICMP) upon which it is based defined in IETF RFC 792. IRDP eliminates the need to manually configure routing information.
Router discovery messages
To enable router discovery, the IRDP defines two kinds of ICMP messages:
* The ICMP Router Solicitation message is sent from a computer host to any routers on the local area network to request that they advertise their presence on the network.
* The ICMP Router Advertisement message is sent by a router on the local area network to announce its IP address as available for routing.
When a host boots up, it sends solicitation messages to IP multicast address 224.0.0.2.
In response, one or more routers may send advertisement messages. If there is more than one router, the host usually picks the first message it gets and adds that router to its
routing table
In computer networking, a routing table, or routing information base (RIB), is a data table stored in a router or a network host that lists the routes to particular network destinations, and in some cases, metrics (distances) associated with th ...
. Independently of a solicitation, a router may periodically send out advertisement messages.
These messages are not considered a routing protocol, as they do not determine a routing path, just the presence of possible gateways.
Extensions
The IRDP strategy has been used in the development of the
IPv6
Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), the communications protocol that provides an identification and location system for computers on networks and routes traffic across the Internet. IPv ...
neighbor discovery protocol.
These use
ICMPv6
Internet Control Message Protocol version 6 (ICMPv6) is the implementation of the Internet Control Message Protocol (ICMP) for Internet Protocol version 6 (IPv6). ICMPv6 is an integral part of IPv6 and performs error reporting and diagnostic fu ...
messages, the IPv6 analog of ICMP messages. Neighbor discovery is governed by IETF standards RFC 4861 and RFC 4862.
IRDP plays an essential role in mobile networking through IETF standard RFC 3344.
This is called
MIPv4 ''Agent discovery''.
See also
*
Dynamic Host Configuration Protocol
References
External links
* {{IETF RFC, 1256, link=no: ICMP Router Discovery Messages
Internet Standards
Internet protocols